Data centers commonly provide computational resources to their users in the form of online data storage and/or data processing services. Users often store their valuable data and run their critical software applications at such data centers. Data centers commonly employ virtual machines to provide data processing services to their tenants. As is known, a “virtual machine” is a software implementation of a physical computing machine, which may appear on a network as a distinct computer but may in fact be one of multiple virtual machines running on a single server. Virtual machines are popular in data centers because they are readily transportable between physical servers and thus promote load balancing and the capability to failover from one physical server to another.